/hwen, wen/ ; unstressed /hweuhn, weuhn/ , adv.
1. at what time or period? how long ago? how soon?: When are they to arrive? When did the Roman Empire exist?
2. under what circumstances? upon what occasion?: When is a letter of condolence in order? When did you ever see such a crowd?
conj.
3. at what time: to know when to be silent.
4. at the time or in the event that: when we were young; when the noise stops.
5. at any time; whenever: He is impatient when he is kept waiting.
6. upon or after which; and then: We had just fallen asleep when the bell rang.
7. while on the contrary; considering that; whereas: Why are you here when you should be in school?
pron.
8. what time: Till when is the store open?
9. which time: They left on Monday, since when we have heard nothing.
n.
10. the time of anything: the when and the where of an act.
[ bef. 1000; ME when ( ne ), OE hwenne; c. G wann when, wenn if, when (cf. Goth hwan when, how); akin to WHO, WHAT ]